This invention relates generally to the field of telecommunications, and more particularly to a rate adjustable backplane and method for a telecommunications node.
The Internet has dramatically increased the potential for data, voice, and video services for customers. Existing circuit-switch telephony systems, however, do not provide the foundation to support the growing need for bandwidth and new services required by both residential and business consumers. As a result, integrated access devices have been introduced to support Internet and related technologies as well as standard telephony service.
Integrated access devices are typically implemented in a card shelf configuration with functionality of the device distributed between discrete line and switch cards connected over a backplane. The line cards provide the service interfaces for the different traffic types and accordingly operate at different rates. For example, a line card providing a plain old telephone service (POTS) interface operates at low speeds on the order of 64 Megabits per second (Mb/s) while a line card for a synchronous optical network (SONET) link, such as a OC-48 link, operates at high speed on the order of 2.5 Gigabits per second (Gb/s).
To support line cards of different rates, backplanes are typically designed to support a full array of high speed line cards. This allows high and low speed line cards to be used in every slot of the integrated access device. Circuitry on the backplane to support the high speed cards, however, can be prohibitively expensive for many low-cost applications in which access devices are utilized. Moreover, while devices with backplanes designed to support only low speed cards can be utilized in these applications, such devices cannot be later upgraded to support high speed interfaces.
The present invention provides a rate adjustable backplane and method for a telecommunications node that substantially eliminates and reduces disadvantageous and problems associated with previous systems and methods. In particular, the backplane includes a low speed bus that terminates at a multiple format switch card and a high speed bus that terminates at an optional high capacity switch card. Circuitry for implementing a high speed communication connection is provided on high speed line cards and the high capacity switch card in order to support low speed applications at low cost and to allow upgrades to higher capacity applications.
In accordance with one embodiment of the present invention, a rate adjustable backplane includes a set of switch slots configured to receive one or more switch cards forming a switch core and a plurality of line slots each configured to receive a line card. A low speed bus couples the line slots to the set of switch slots. A high speed bus also couples the line slots to the set of switch slots. Each line slot includes a low speed connector coupled to the low speed bus and a high speed connector coupled to the high speed bus. The low speed connector is adapted to receive a mating connector of a line card to establish a low speed communication connection between the line card and the switch core. The high speed connector is adapted to receive a mating connector of a line card to establish a high speed communication connection between the line card and the switch core.
More specifically, in accordance with a particular embodiment of the present invention, the set of switch slots includes a first switch slot adapted to receive a low capacity switch card and a second switch slot adapted to receive a high capacity switch card. A unibus couples the first and second switch slots together. In this and other embodiments, the low speed bus may comprise a time division multiplex (TDM) bus and the high speed bus may comprise an asynchronous transfer mode (ATM) bus. ATM cells may be transported in asynchronously fixed, synchronous or other suitable cell slots.
In accordance with another aspect of the present invention, a high speed communication connection is established between a line card and a switch core over a backplane of a telecommunications node by establishing a communication connection between the line card and the switch core over a low speed bus operating at a predefined rate. A high speed rate at which to operate a point-to-point link of a high speed bus coupling the line card to the switch core is determined. The high speed bus is then operated at the defined rate to communicate traffic between the line card and the switch core.
Technical advantages of the present invention include providing an improved backplane for a telecommunications node. In particular, the backplane is rate adjustable to support low capacity applications at low cost and ungradable with the addition of high speed line cards and a high capacity switch card to support high capacity applications. As a result, system costs are more directly proportional to functionality which allows low-cost solutions for low-rate and other limited applications.
Another technical advantage of the present invention includes providing a distributed bus architecture for a backplane of a telecommunications node. In particular, a low speed TDM bus and a high speed ATM bus are provided between each line card and a switch core. The low speed bus and the high speed bus each include point-to-point links between the line cards and the switch core to provide signal robustness and allow each high speed link to operate at a different rate. High speed line cards use the low speed telephony subscriber bus as a data link to establish a rate with which to communicate service traffic with the switch core over the high speed bus. Thus, the backplane provides a robust communication structure, supports high and low speed line cards in each slot of the telecommunication node to maximize flexibility, and allows high speed line cards to set the rate of their connection to the switch core.
Other technical advantageous of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.